I want also to add that it's chromium fault, not vivaldi's, all chromium 64 based browsers, as already said in other threads, suffer the same problem. The fix should be provided by chromium, and probably it will be in next snapshots.

Having the same issue, but am not running a snapshot. Using 1.14 stable. I only install updates when Vivaldi notifies me. Do I need to roll back to 1.13, as well? (And, if so, will that gank and settings/preferences/extensions?)